Known in prior art are capacitive sensor devices for detecting a contact by an object with a detection surface. Such sensor devices also are known as capacitive touch sensors. Furthermore, known in prior art are capacitive sensor devices for detecting a movement of an object relative to a detection surface. These sensor devices also are known as capacitive movement sensors.
Contacts with a detection surface, for example by a finger, may be detected by means of the capacitive touch sensors, while movements of a finger relative to a detection surface and in a certain distance from the detection surface may be detected by means of capacitive movement sensors.
In this connection it is desired to detect contacts by a finger at a detection surface as well as movements of the finger in front of the detection surface relative to the detection surface. To do so, a sensor device may be provided, which comprises a capacitive touch sensor as well as a capacitive movement sensor. Both the capacitive touch sensor and the capacitive movement sensor each have a number of sensor electrodes by means of which a contact and a movement are detected, respectively. The sensor electrodes of the touch sensor and of the movement sensor are arranged relative to the detection surface such that in a certain area of the detection surface, preferably in the whole area of the detection surface, both a contact with the detection surface as well as a movement relative to the detection surface may be detected.
In order to detect both a contact as well as a movement by means of the respective capacitive sensor it may be required to operate the capacitive touch sensor and the capacitive movement sensor within different time intervals, so that in one instant of time always only one of the two capacitive sensors is active. In order to detect a contact as well as a movement ideally at the same time it may be advantageous to switch back and forth between the operation of the touch sensor and of the movement sensor within relatively short time intervals. This is to mean that when the touch sensor is active the movement sensor is inactive and vice versa.
However, switching over from the touch sensor to the movement sensor has the disadvantage that the output signal and the sensor signal, respectively, of the movement sensor has a relatively long settling phase immediately after the activation of the movement sensor, which may last several seconds, so that the sensor signal of the movement sensor in the worst case only may be evaluated correctly after several seconds. Settling times comprising durations that long are not acceptable for practical applications, in particular when a signal processing has to be carried out in real-time.
However, this problem also occurs when another sensor device is used instead of a touch sensor.